Advances in magnetic recording head technology are often drive by a desire to increase the areal density in the hard drive, which is the number of bits that can be written and/or read to the storage medium in a given length, area, or volume. One method that has been utilized to increase the areal density is heater-based actuation of the magnetic transducer. Heater-based actuation of the transducer has allowed hard drive designers to attain smaller spacing between the transducer and the magnetic media, thereby increasing the areal density.
When heater-based actuation is utilized, new engineering challenges to balance reliability with the performance increase arrive. Before heater-based actuation, the spacing goal to maximize areal density was relatively clear: set the slider fly targets as low as possible while still ensuring sufficient reliability. When using heater-based actuation, minimizing the zero-heat (or “passive”) clearance isn't as important and instead, the optimal fly height is one where the lowest flying heads still require heater actuation to reach the operating (or “active”) clearance target while the highest flying heads don't require so much heat as to violate temperature reliability limits. Further advances in transducer design may allow this goal to be attained.